Electrolytic cells have been used as optical devices. These cells provide a pair of electrodes in the form of a molecular metallic layer on a dielectric substrate, the electrodes being separated by an electrolyte containing metallic ions such as silver. An electrical pulse applied across the electrodes causes the silver ions to plate out on one of the electrodes, changing the opacity of the electrode surface. The plating process can be made reversible by reversing the polarity of an applied voltage pulse. Such an optical device is described, for example, in the article "An Experimental Display Structure Based on Reversible Electrodeposition" by Camlibel, Singh, Stocker, Van Uitert, and Zydzik, Applied Physics, Letter 33(9), Nov. 1, 1978. Such cells have heretofore been of interest because of their optical properties. Such cells operate by electrodepositing an opaque layer of metal out of a transparent electrolyte. The process can be made reversible by changing the polarity of the voltage across the cell, resulting in a device which can be switched between an optically transparent and an optically opaque condition. Applicant has found that the electrodeposition of metal ions from an electrolyte can also be used to change the electrical resistivity of cell electrodes, giving rise to a device which can be used as an electrical switching device over a wide frequency band including dc.
In brief, the present invention provides a cell having two electrode surfaces separated by an electrolyte. By applying an electrical pulse across the electrodes, metal ions are plated out on one or the other of the electrodes to sufficient thickness to reduce the electrical resistivity of the electrode surface from a relatively high value to a very low value. Thus the device can be used to change the electrical resistivity of a current path between two terminals embedded in one or both the electrodes. A reverse polarity pulse returns the device to its original state.
The electrical resistance may be varied over a wide range of values. As a nonmechanical electro-chemical switch, it is capable of almost limitless cycles of operation without failure.